Up to one in five men carries a version of the male chromosome that greatly increases their risk of heart disease, scientists claimed Thursday.

University of Leicester researchers studied over 3,000 British men's DNA and found that 90 percent of male chromosomes belonged to two major groups—one of which, haplogroup I, increases the risk of coronary artery disease by 50 percent.

Dr. Maciej Tomaszewski, the team's lead researcher, said it was likely that the increased risk was caused by the gene's influence on the immune system and inflammatory responses.

"The human Y chromosome appears to play a role in the cardiovascular system beyond its traditionally-perceived determination of male sex," Tomaszewski said.

The results of the four-year study, which was published in The Lancet, found that the increased risk for men carrying the haplogroup I version of the Y chromosome was independent of factors like high cholesterol, high blood pressure and smoking.

Dr. Helene Wilson, from the British Heart Foundation, which partly-funded the study, said, "This study shows that genetic variations on the Y chromosome—the piece of DNA that only men have—can greatly increase a man's risk of coronary heart disease."

She added, "Lifestyle choices such as poor diet and smoking are major causes, but inherited factors carried in DNA are also part of the picture. The next step is to identify specifically which genes are responsible and how they might increase heart attack risk."

The foundation hoped that the discovery could lead to new treatments for heart disease in men or the development of tests that could identify men at high risk of a heart attack.

In the U.S., heart disease is the top cause of death of both men and women, but men's risk begins at a younger age.